In recent years, there is a strictly increasing demand for reducing a fuel consumption in automobiles from a standpoint of saving resources and conserving the environment. As for automobile tires, the reduction of rolling resistance is desired for the reduction of a fuel consumption. The reduction of rolling resistance is generally achieved by using a rubber material capable of giving a vulcanized rubber exhibiting a reduced heat build-up.
Recently it has been proposed to use a rubber composition comprising silica as a reinforcer and a diene rubber having introduced therein a substituent having affinity to silica, for lowering the heat build-up. As examples of the substituent having an affinity with silica, which is introduced in a diene rubber, there can be mentioned a tertiary amino group (Japanese Unexamined Publication No. 1-101344 and ibid. 64-22940), an alkyl-silyl group (Japanese Unexamined Patent Publication No. 1-188501) and a halogenated silyl group (Japanese Unexamined Patent Publication No. 5-230286). However, the reduction of heat build-up by the rubber composition comprising silica and a diene rubber having introduced therein a substituent having an affinity with silica is not to a sufficient extent, and tensile properties such as tensile stress and abrasion resistance are poor.